[dune-fem] Building stiffness matrix

[Mauro Pagani]

Hi,



I have a problem about solving the equation

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ε*ε ∂tv + 4v(v*v-1) - 0.5*ε*ε div M v= 0

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I manage to arrive to modelize this with Euler method, but I don't understand how to calculate Stiffness Matrix
of the form:

Sij = \intK ((M φj)φi) dx

With K a right triangle (dimensions h x h) of the grid and M the coefficient of anisotropy (in more dimensions this become a diagonal square matrix).

I know that S is symmetric, but not diagonal: so to build it I need to have a node and all its neighbours...how could I implement this?

Thank you for your help,

Mauro Pagani



  		 	   		  
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